Abstract
This paper investigates the flexural behavior of reinforced recycled aggregates concrete (RRAC) beams after exposed
to high temperatures. The experimental results from 17 specimens were present and compared with temperatures, recycled coarse aggregate (RCA) replacement percentages, and concrete strength as variables. It was found that the high temperature would not cause an observable change in the failure pattern. However, high temperature can significantly reduce the stiffness and ductility, and accelerate the damage degradation of specimens. After exposure to 600oC, the ultimate bearing capacity of the specimens decreased by 20%-30% The mechanical properties of RRAC beams after high temperatures were barely impacted by the replacement percentages. Increasing the concrete strength of RCA could effectively improve the bearing capacity and peak deflection of RRAC beams after exposed to high temperatures. Furthermore, the calculation method of the bending bearing
capacity and deflection of RRAC beams was also discussed.
Key Words
beams; flexural behavior; high temperature; recycled aggregates concrete
Address
Longshou Qin: College of Civil Engineering and Architecture, Guangxi University, Nanning, 530004, P.R. China; Guangxi Hualan Engineering Management Co., Ltd., Nanning, 530011, P.R. China
Xian Li: College of Civil Engineering and Architecture, Guangxi University, Nanning, 530004, P.R. China
Ji Zhou: College of Civil Engineering and Architecture, Guangxi University, Nanning, 530004, P.R. China
Ying Liang: College of Architecture and Civil Engineering, Nanning University, Nanning, 530200, P.R. China
Wangsheng Ou: College of Architecture and Civil Engineering, Nanning University, Nanning, 530200, P.R. China
Zongping Chen: College of Civil Engineering and Architecture, Guangxi University, Nanning, 530004, P.R. China; College of Architecture and Civil Engineering, Nanning University, Nanning, 530200, P.R. China
Abstract
The structural health of a pipeline is usually assessed by visual inspection. In addition to the fact that this method is expensive and time consuming, inspection of the whole structure is not possible due to limited access to some points. Therefore, adopting a damage detection method without the mentioned limitations is important in order to increase the safety of the structure. In recent years, vibration-based methods have been used to detect damage. These methods detect structural defects based on the fact that the dynamic responses of the structure will change due to damage existence. Therefore, the location and extent of damage, before and after the damage, are determined. In this study, fuzzy genetic algorithm has been used to monitor
the structural health of the pipeline to create a fuzzy automated system and all kinds of possible failure scenarios that can occur for the structure. For this purpose, the results of an experimental model have been used. Its numerical model is generated in ABAQUS software and the results of the analysis are used in the fuzzy genetic algorithm. Results show that the system is more accurate in detecting high-intensity damages, and the use of higher frequency modes helps to increase accuracy. Moreover, the
system considers the damage in symmetric regions with the same degree of membership. To deal with the uncertainties, some error values are added, which are observed to be negligible up to 10% of the error.
Key Words
damage detection; fuzzy genetic system; natural frequency; pipeline health monitoring
Address
Amirmohammad Jahan, Mahdi Mollazadeh, Abolfazl Akbarpour and Mohsen Khatibinia: Department of Civil Engineering, University of Birjand, Birjand, Iran
Abstract
Urbanization and industrialization have significantly increased the amount of solid waste produced in recent decades, posing considerable disposal problems and environmental burdens. The practice of waste utilization in concrete has gained popularity among construction practitioners and researchers for the efficient use of resources and the transition to the circular economy in construction. This study employed Lytag aggregate, an environmentally friendly pulverized fuel ash-based
lightweight aggregate, as a substitute for natural coarse aggregate. At the same time, fly ash, an industrial by-product, was used as a partial substitute for cement. Concrete mix M20 was experimented with using fly ash and Lytag lightweight aggregate. The percentages of fly ash that make up the replacements were 5%, 10%, 15%, 20%, and 25%. The Compressive Strength (CS), Split Tensile Strength (STS), and deflection were discovered at these percentages after 56 days of testing. The concrete cube, cylinder, and beam specimens were examined in the explorations, as mentioned earlier. The results indicate that a 10% substitution of cement with fly ash and a replacement of coarse aggregate with Lytag lightweight aggregate produced concrete that performed well in terms of mechanical properties and deflection. The cementitious composites have varying characteristics as the environment changes. Therefore, understanding their mechanical properties are crucial for safety reasons. CS, STS, and deflection are the essential property of concrete. Machine learning (ML) approaches have been necessary to predict the CS of concrete. The Artificial Fish Swarm Optimization (AFSO), Particle Swarm Optimization (PSO), and Harmony Search (HS) algorithms were investigated for the prediction of outcomes. This work deftly explains the tremendous AFSO technique, which achieves the precise ideal values of the weights in the model to crown the mathematical modeling technique. This has been proved by the minimum, maximum, and sample median, and the first and third quartiles were used as the basis for a boxplot through the standardized method of showing the dataset. It graphically displays the quantitative value distribution of a field. The correlation matrix and confidence interval were represented graphically using the corrupt method.
Address
S. Sivakumar: Department of Civil Engineering, PSNA College of Engineering and Technology, Dindigul, 624622, India
R. Prakash: Department of Civil Engineering, Government College of Engineering, Tirunelveli, 627007, India
S. Srividhya: Department of Civil Engineering, VaruvanVadivelan Institute of Technology, Dharmapuri, 636701, India
A.S. Vijay Vikram: Department of Civil Engineering, Global Institute of Engineering and Technology, Vellore, 632509, India
Abstract
A novel combinatorial type-2 adaptive neuro-fuzzy inference system (T2-ANFIS) and robust proportional integral
derivative (PID) control framework for intelligent vibration mitigation of uncertain structural system is introduced. The fuzzy logic controllers (FLCs), are designed independently of the mathematical model of the system. The type-1 FLCs, have a limited ability to reduce the effect of uncertainty, due to their fuzzy sets with a crisp degree of membership. In real applications, the consequent part of the fuzzy rules is uncertain. The type-2 FLCs, are robust to the fuzzy rules and the process parameters due to the fuzzy degree of membership functions and footprint of uncertainty (FOU). The adaptivity of the proposed method is provided with the optimum tuning of the parameters using the neural network training algorithms. In our approach, the PID control force is obtained using the generalized type-2 neuro-fuzzy in such a way that the stability and robustness of the controller
are guaranteed. The robust performance and stability of the presented framework are demonstrated in a numerical study for an eleven-story seismically-excited building structure combined with an active tuned mass damper (ATMD). The results indicate that the introduced type-2 neuro-fuzzy PID control scheme is effective to attenuate plant states in the presence of the structured and unstructured uncertainties, compared to the conventional, type-1 FLC, type-2 FLC, and type-1 neuro-fuzzy PID controllers.
Key Words
soft computing; the footprint of uncertainty; type-2 FLC; type-2 neuro-fuzzy PID; uncertainty
Address
Javad Palizvan Zand, Javad Katebi and Saman Yaghmaei-Sabegh: Faculty of Civil Engineering, University of Tabriz, Tabriz, Iran
Abstract
Engineering structures usually suffer from cracks. The crack geometry has an influence on the structural mechanical properties and subsequent crack propagations. However, as an extensively utilized method in fracture analysis, the extended
finite element method provided by Abaqus fails to output the specific location and dimensions of fractures. In this study, a technique to capture the crack geometry is proposed. The technique is based on the invariant level set method (I-LSM), which can avoid updating the level set function during crack development. The solution is achieved by an open-source plug-in programmed by Python. Three examples were performed to verify the effectiveness and robustness of the program. The result shows that the developed program can accurately output the crack geometry in both the 2D and 3D models. The open-source plug-in codes are included as supplementary material.
Key Words
Abaqus; crack geometry; developed program; extended finite element method; I-LSM
Address
Tao Wang, Shangtao Hu, Menggang Yang: School of Civil Engineering, Central South University, Changsha, 410075, China; National Engineering Research Center of High-speed Railway Construction Technology, Central South University,
Changsha, 410075, China
Shujun Fang: School of Civil Engineering, Central South University, Changsha, 410075, China
Abstract
Spatial cable systems can provide more transverse stiffness and torsional stiffness without sacrificing the vertical bearing capacity compared with conventional vertical cable systems, which is quite lucrative for long-span earth-anchored suspension bridges' development. Higher economy highlights the importance of refined form-finding analysis. Meanwhile, the internal connection between the lateral and vertical sags has not yet been specified. Given this, an analytic algorithm of formfinding for the earth-anchored suspension bridge with spatial cables is proposed in this paper. Through the geometric compatibility condition and mechanical equilibrium condition, the expressions for cable segment, the recurrence relationship between catenary parameters and control equations of spatial cable are established. Additionally, the nonlinear general reduced gradient method is introduced into fast and high-precision numerical analysis. Furthermore, the analytic expression of the lateral and vertical sags is deduced and discussed. This is very significant for the space design above the bridge deck and the optimization of the sag-to-span ratio in the preliminary design stage of the bridge. Finally, the proposed method is verified with the aid of two examples, one being an operational self-anchored suspension bridge (with spatial cables and a 260 m main span), and the other being an earth-anchored suspension bridge under design (with spatial cables and a 500 m main span). The necessity of an iterative calculation for hanger tensions on earth-anchored suspension bridges is confirmed. It is further concluded that the main cable and their connected hangers are in very close inclined planes.
Key Words
earth-anchored suspension bridge; hanger force iteration; lateral sag; vertical sag; multi-segment catenary;
spatial cables
Address
Gen-min Tian, Wen-ming Zhang, Jia-qi Chang and Zhao Liu: Key Laboratory of Concrete and Prestressed Concrete Structures of the Ministry of Education, Southeast University, Nanjing, China
Abstract
Concrete construction, one of the oldest building practices, is commonly used in all parts of the world. Concrete is the primary building material for both residential and commercial constructions. The challenge of protecting the buildings, hence nation, against the attack of terrorism has raised the importance to explore the understanding of building materials against the explosion. In this research, a security check-post (reinforced concrete frame filled with plain cement concrete) has been chosen to study the behavior of structural elements under blast loading. Eight nitroglycerines-based dynamite blasts with varying
amounts of explosive charge, up to 17 kg weight has been carried out at various scale distances. Pressure and acceleration time history records are measured using blast measuring instruments. Security check post after being exposed by explosive loading are photographed to view cracking/failure patterns on the structural elements. It is noted that with the increase of quantity of explosive, the dimensions of spalling and crack patterns increase on the front panels. Simple empirical analyses are conducted
using ConWep and other design manuals such as UFC 3-340-02 (2008) and AASTP-1 (2010) for the purpose of comparison of blast parameters with the experimental records. The results of experimental workings are also compared with earlier researchers to check the compatibility of developed equations. It is believed that the current study presents the simple and preliminary procedure for calculating the air blast and ground shock parameters on the structures exposed to blast explosion.
Key Words
air blast; charge; explosion; ground shock; scaled range
Address
Muhammed Rizvan Akram: Department of Civil Engineering, Gebze Technical University, 41400 Kocaeli, Turkey
Ali Yesilyurt: Department of Earthquake Engineering, Istanbul Technical University, 34469, Istanbul, Turkey
Abstract
Free-vibration and buckling analyses of plate problems are investigated with the aid of the strain gradient notation
finite element method (SGN-FEM). As SGN-FEM employs physically interpretable polynomials in developing finite elements, parasitic shear sources, which are the cause of shear locking, can be precisely identified and subsequently eliminated. This allows two mutually complementary objectives to be defined in this work, namely, evaluate the efficiency of free-vibration and buckling results provided by corrected models, and study the severity of parasitic shear effects on plate models performance. Parasitic shear are flexural terms erroneously present in shear strain polynomials. It is reviewed here that six parasitic shear terms arise during the formulation of the four-node Mindlin plate element. Two parasitic shear terms have been identified in the in-plane shear strain polynomial while other two have been identified in each of the transverse shear strain polynomials. The element is corrected a-priori, i.e., during development, by simply removing the spurious terms from the shear strain polynomials. The computational implementation of the element in its two versions, namely, containing the parasitic shear terms (PS) and corrected for parasitic shear (SG), allows for assessments of the accuracy of results and of the deleterious effects of parasitic shear in free vibration and buckling analyses. This assessment of the parasitic shear effects is a novelty of this work. Validation of the SG model is done comparing its results with analytical results and results provided by other numerical procedures. Analyses are performed for square plates with different thickness-to-length ratios and boundary conditions. Results for thin plates provided by the PS model do not converge to the correct solutions, which indicates that parasitic shear must be eliminated. That is, analysts should not rely on refinement alone. For thick plates, PS model results can be considered acceptable as deleterious effects are really critical in thin plates. On the other hand, results provided by the SG model converge well for both thin and thick plates. The effectiveness of the SG model is established via high-accuracy results obtained in several examples. It is concluded that corrected SGN-FEM models are efficient alternatives for free-vibration and buckling analysis of Mindlin plate problems, and that precise elimination of parasitic shear is a requirement for sound analyses.
Key Words
buckling; finite element method; free vibration; Mindlin plate; parasitic shear; shear locking; strain gradient notation
Address
Leilson J. Araujo and João E. Abdalla Filho: Graduate Program in Civil Engineering, Federal University of Technology-Parana, Rua Deputado Heitor Alencar Furtado, 5000, Curitiba, PR 81280-340, Brazil
